Growing Bulbs Outdoor or Indoors

Planning your bulb garden

Bulb cultivation

Botanically, bulbs are buds, commonly subterranean, producing roots from their undersides, and consisting of layers of fleshy rudimentary leaves, called scales, attached to abbreviated stems. There is considerable uncertainty in the minds of many gardeners as to the difference between bulbs, corms, rhizomes and tubers, for their function is the same to tide the plant over a period of adverse conditions, such as summer droughts and winter cold. All have common factors: food storage; rapid growth under suitable conditions; and the same life-cycle, in that during growth and flowering, next year’s flower is formed in miniature, the foliage soon reaching maturity and dying away, as do the roots in most cases when the whole plant enters a period of rest.

A true bulb, such as that of a tulip, hyacinth or narcissus, is a bud surrounded by fleshy or scaly leaves, arising from a flat disc of ‘basal plate’. In `tunicated’ bulbs the fleshy leaves are rolled close together, as in the tulip. In ‘imbricated’ bulbs the bulb leaves are thick and overlapping, as in the lily.

The determination of whether or not a particular plant is a bulb depends upon the structure of the storage organ. If the botanical definition of the bulb is strictly accepted, many plants that gardeners ordinarily consider bulbs, such as crocuses, calla lilies, cannas and dahlias, must be eliminated. These and many other plants not technically true bulbs have bulb-like organs that function in the same way as bulbs but are not structurally scaly buds. They include rounded or flattish, solid, swollen stem bases called corms as in gladioli, crocuses; elongated thickened stems called rhizomes as in cannas, calla lilies, lily-of the-valley; thickened terminal portions of stems called tubers as in anemones, begonias, caladiums; and swollen tuber-like roots as in dahlias.


Nearly all bulbs produce offsets sooner or later, and these, except for rarities, give sufficient stock for the ordinary gardener. All that needs to be done is to dig up the clumps, separate the bulbs, sort out the small ones and replant them, treating them like mature bulbs until they reach the flowering stage. Rhizomes and tuberous roots may be treated in the same way, so each eye will produce another plant if care is taken of it. The exceptions are erythroniums, which rarely produce offsets, and cyclamen, which never do, and therefore can only be increased from seeds.

This leads to a consideration of raising bulbs from seed. Except for the most enthusiastic of amateurs, this should be left to the specialist. Where seed is produced, it is easy to obtain a supply, but the seed of many bulbs does not come true. That is the seedlings raised have characteristics which differ from their parents. There is also the question of cross fertilization to take into account, and, of course, raising bulbs from seed is a lengthy undertaking, often a risky one as well. However, with these provisos, it may be said that raising lilies from seed is an interesting process.

Corms replace themselves annually. After having thrown up its leaves and flowers, each corm shrivels away and a new corm, sometimes several, forms while the leaves and flowers of the old one are growing.

Without bulbs all gardens would be poorer the whole year round, but particularly in autumn, spring and summer Bulbs are so popular because they yield such big rewards for so little in terms of money and care. Bulbs make it possible to have a continuous succession of color outdoors and indoors throughout the year. Bulbs will flourish in virtually any kind of well-drained soil. Bulbs will thrive in almost every conceivable position or situation in the garden, in sun or partial shade. Bulbs offer infinite variety in color, form and texture. When in bloom they vary from an inch or two in height to several feet and the characteristics of their foliage are as diverse as their flowers. The flowers of most bulbs last well when cut and are ideal for flower arrangements. Gardening with bulbs requires a minimum of work. Bulbs are easy to cultivate, giving a high percentage of successful results even for the beginner. Bulbs are not only inexpensive but are easily obtainable.


Always purchase good-size, healthy bulbs from a reputable dealer. Early ordering is vital to ensure the best selection. Plant immediately when the bulbs arrive and if this is inconvenient open the bags for ventilation and keep the bulbs in a cool, dry place until you are ready to plant them. Plant in well-drained soil. The vast majority of bulbs will do well in any soil provided it is well drained. It is advisable, however, to treat heavy soils with applications of peat or well-rotted leaf mold.

The planting period for bulbs will depend upon their flowering season. The planting period for spring-flowering bulbs extends from September 1 to December 15 in the Northern Hemisphere, but daffodils should be planted before the end of October. Autumn-flowering bulbs (crocus and colchicum) should be planted in August. Most summer-flowering bulbs should be planted in March and April, although some, such as lilies, should be planted in November and December. Stem-rooting lilies can also be successfully set out in early spring.

Plant bulbs at the right depth.

Although there are exceptions, bulbs are generally set with their tops about three times the diameter of the bulb below ground; small bulbs proportionately deeper. Usually, it is the pointed end of the bulb which should be uppermost, but some tubers are planted horizontally. Some bulbs, such as anemones, give no indication of which end is up, but there are usually signs of previous stem or root sources. Spring-flowering bulbs such as hyacinths, daffodils and tulips are planted 16cm (6in) deep and most spring-flowering small or miscellaneous bulbs are planted 8-10cm (3-4in) deep. Variation in depth depends upon the height of the stem and on the type of soil—the longer the stem and the lighter the soil, the deeper the planting.

No general guidance can be given on spacing of bulbs, for this may range from 2.5cm (1 in) to 0.6m (2ft) apart, depending upon the size of the plant, its flower and foliage. Bulbs planted in groups or clusters produce the best effects, and if flowers are wanted for indoor decoration extra bulbs should be planted in the vegetable garden or special cutting garden.

Bulbs can be grown virtually anywhere in the garden. There is a place in every garden for some kinds of bulbs in beds, borders, edges, shrubberies, rock gardens, orchards, woodlands, lawns, on walls, between paving stones, in tubs or window-boxes. Many bulbs can be naturalized, that is, planted in informal groups or drifts and left to increase naturally. This is often done in rough grass or woodland, The grass should be left uncut until the bulb foliage has died down naturally, usually in June.

Most bulbs do not require full sun but can be planted in partial shade. Indeed, partial shade makes for longer lasting blooms. Flowers should be removed when petals fade and the foliage should not be cut off, but should be allowed to die down naturally, permitting the bulb to replace energy and flower the following season. Most spring-flowering bulbs (the exceptions are lilies, anemones and ranunculuses which require winter protection) should be lifted. Lift bulbs carefully only after the foliage has died down and store them in a cool, frost-free and well-ventilated place until it is time to replant them again. Generally, if bulbs are doing well, natural increase will make lifting of the clumps and separation of the bulbs necessary every few years. Be careful when separating clumps of bulbs not to damage them. Bulbs should always be handled carefully to avoid physical injury.

The most commonly grown bulb flowers in our gardens are narcissi, tulips and hyacinths, with lilies, snowdrops, grape hyacinths and several others also represented in the list.

Daffodil is merely the common name for narcissus, of which there are more than 10,000 named varieties, with some 500 in normal commercial cultivation.

With the exception of one or two kinds, such as tazettas, narcissi are hardy, tolerant and adaptable plants. They will grow in almost any situation except heavy shade or in badly-drained soil. In open ground they flower from February to the end of May. Normally most varieties remain in flower for three to four weeks and if they are picked in bud for cut flowers they will last in water for ten days or more.

Narcissi will flourish in beds and borders, naturalized in meadows, open woodlands, lawns, orchards or under scattered trees, among shrubs, in tubs and window boxes. The smaller kinds do well in rock gardens and many varieties are suitable for forcing.

Out of doors daffodils will flourish in any well-drained soil although N. bulbocodium prefers sandy soil and N. cyclamineus peaty soil. The best sites are in sun or light shade with shelter from sweeping winds. Plant the bulbs as early in the autumn as they can be obtained Robust kinds that have large bulbs should be planted 13-16cm (5-6in) deep, less vigorous kinds with smaller bulbs 8-10cm (3-4in) deep, and tiny species 8cm (3in) deep. Space vigorous growers 16-23cm (6-9in) apart, moderately vigorous growers 10-13cm (4-5in) apart, and small species 6-10cm (2-4in) apart. In naturalized plantings, these distances are varied considerably and it is best to scatter the bulbs at random, in groups or drifts, planting them exactly where they fall.

For planting bulbs out of doors, especially in turf, special planting tools are available. Some of these are long-handled tools, shod with a circular metal cutter which is forced into the soil. When the tool is lifted a core of turf and soil is removed intact. A bulb is then placed in the hole and the core of turf replaced over it and firmed with the foot. To enable the cutter to be driven easily into hard turf the tool is fitted with a foot bar. There are versions of this tool with short handles, without the foot bar. Otherwise, when planting in soil or in the rock garden it is always advisable to do so with a trowel, never with a dibber. If a dibber is used an air pocket may be left below the bulb, into which the roots will not grow, thus preventing proper development. If the soil is dry, water thoroughly after planting.

Where winters are severe, protect bulbs which are not planted in grass with a covering of leaves or other suitable material. Feed established plantings in early autumn and early spring, using a complete fertilizer in spring and a slower-acting organic fertilizer in the autumn Water copiously during dry spells when the foliage is above ground. Never remove the foliage until it has died down naturally. When plantings become crowded so that the bloom deteriorates in quantity and quality, lift, separate and replant the bulbs as soon as the foliage has died down.

Tulips are equally numerous, with several thousand named varieties and some 800 in commercial cultivation. They differ more than narcissi and are divided into 23 main groups of classes, of interest mainly to the specialist.

Some tulips flower early (in mid-April, some in mid-season (late April), and others bloom late, in May. The color range is from white to almost black, from softest pink to deepest purple; there are broken colors, self-colors, striped, streaked, shaded and tinged. Some have oval flowers, some are shaped like turbans, and others are square at the base. Some tulips resemble paeonies, others have lily-like flowers. There are tulips with fringed or curled petals and others with pointed petals. A number produce several flowers on a stem. Some have tiny flowers, while others produce blooms up to 38cm (15in) in diameter. Heights range from a few cm to nearly 1 m (3ft).

Cultivation Bulbs can be planted out of doors between mid-September and mid-December. Species or botanical tulips should be planted 10cm (4in) deep and about 13cm (5in) apart with the exception of T. fosteriana, which should be planted 13-16cm (5-6in) deep and some 16cm (6in) apart, like all divisions of garden tulips. Good drainage is essential; they will thrive in virtually any well-drained soil, but in light sandy soils the bulbs should be planted a little deeper than normal. Tulips can be interplanted with roses or with annuals or with other bulbs flowering at the same time, taking into account the differing heights of other plants when interplanting. Species tulips do best in sunny positions, but garden tulips can be planted in sun or in partial shade. Early-flowering garden tulips planted in sheltered sunny spots will come into flower sooner, or if late-flowering tulips are planted in partial shade, they will last longer.

Apart from kaufmanniana tulips which are naturalized, all tulips should be lifted every year when the foliage has turned completely yellow and begun to die off. The old flower stems should be cut off a little above the newly formed bulbs at the end of June or early July. They should, under no circumstances, be left on the bulb in storage trays. If the bulbs must be cleared from the ground before the foliage begins to die, to make way for other bedding plants, they may be lifted and heeled into a shallow trench in a spare corner until the leaves yellow. The lifted bulbs should be kept out of sunlight, cleaned and stored in a cool, airy, frost-free place until planting time comes round again. Indoor cultivation is the same procedure as narcissus, but forced tulip bulbs are not really worth keeping for later outdoor planting.

There are far fewer hyacinths than tulips or daffodils, but because of their beauty and their perfume, they continue to be firm favorites for the garden.


Bedding hyacinths are best planted in late October about 10cm (4in) deep in well-drained soil and in a sunny position. Space the bulbs about 20cm (8in) apart for maximum color effect. Bone meal forked into the soil before planting at the rate of 112g (4oz) to the sq m (sq yd) will ensure good heads of flower in April.

Watering, feeding, mulching It is essential for all bulbs to have plenty of moisture when growing actively, but excess water during the dormant period is harmful. Like all plants, bulbs respond to fertile soil, but manures and fertilizers must be used carefully. Well-rotted manure improves soil structure and provides nutrients for all plants and may be used to advantage with bulbs as long as there is a protective layer of soil between the bulbs and the manure. Fresh manure should never be used. Slow-acting fertilizers other than manure are particularly recommended for feeding bulbs. Bonemeal is one of the best and 3kg (61b) to a 11 sq m (100 sq ft) is not too heavy an annual application.

Mulches are useful in the summer to help the soil to retain moisture and peat is excellent for this purpose. Mulches intended for protective winter covering should be applied to the surface of the ground after the ground has frozen and should be removed after bulb growth is underway in the spring.

Weeds, pests, diseases

Areas planted with bulbs should be kept as free of weeds as possible and the surface soil

1. Should be loosened from time to time.

2. Injured or infected foliage should be removed and burned.

Diseases can be avoided by buying only healthy, top quality bulbs, and few gardeners who do this are troubled by diseases.

The major pests are slugs and snails and fortunately, these can be controlled by modern slug killers. In dealing with any diseases or pests, proper diagnosis is important before resorting to drastic measures. Should a disease appear among a planting, lift the healthy bulbs, disinfect them, and move them to an area not previously used for growing bulbs of the same kind. This will usually save them from infection.

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